The present invention relates to a longitudinal road surface profile measurement method for surveying flatness of a plane having irregularities such as a road surface of a road.
Conventionally, as a method for measuring straightness of an object under measurement on a straight line, such a method (hereinafter called sequential-two-points method) has been known for, as disclosed in Japanese Patent Publication No.61-33364 (see FIG. 11), arranging two displacement gages 6 and 7 with a short pitch therebetween toward an object-under-measurement 3 on a slide 4 movably engaged to a straight guide 5 in parallel with the object-under-measurement 3, feeding in one direction the slide 4 over an entire length of a measurement length by the pitch each time, to measure a distance between the two displacement gages 6 and 7 and the object-under-measurement 3 using the displacement gages 6 and 7 respectively at each position, and processing resultant data to thereby obtaining straightness of the straight guide and the object-under-measurement. By this sequential-two-points method, it is possible to obtain straight geometry curves of both the straight guide and the object-under-measurement independently of each other to thereby accurately survey the straightness of the object-under-measurement even if the guide is not straight, which is very convenient.
By this sequential-two-points method, however, it is necessary to always hold in parallel with each other two displacement gages when they are mounted in a vehicle to measure a longitudinal road surface profile, thus suffering from a problem that the measurement is very complicated. Moreover, a recent road employs pavement with drainage and sound absorbance having fine irregularities on a surface thereof, so that it is necessary by the sequential-two-points method to pay attention so that a probe of the displacement gages may not be affected by these irregularities. There is also an auto-collimator method available for moving a reflecting mirror to detect an inclination angle at a movement position and processing it to obtain a longitudinal profile. The auto-collimator method, however, requires much labor in movement of the reflecting mirror, thus suffering from a problem that the measurement is very complicated.
To solve these problems, the present invention has been developed, and it is an object of the present invention to provide a longitudinal road surface profile measurement method that can survey longitudinal flatness of a road surface of a road easily and accurately.
To achieve the object, a first aspect of the present invention provides a longitudinal road surface profile measurement method for surveying longitudinal flatness of a road surface by longitudinally moving a measurement vehicle on a road, comprising the steps of: arranging first, second, and third disk-shaped rollers having the same outer diameter so that the rollers have a predetermined spacing therebetween on the same straight line and rotate in the same straight-line direction; using a measurement block constituted of a first predetermined-length coupling rod which is mounted on rotary shafts of the first and second rollers to couple the first and second rollers in a revolving manner, a second coupling rod which has the same length as the first coupling rod and which is mounted on rotary shafts of the second and third rollers to couple the second and third rollers in a revolving manner, distance measurement means which measures a movement distance of the rollers, and angle detection means which detects a displacement angle by which the first and second coupling rods have revolved from a straight state thereof, to elastically couple the measurement block to a measurement vehicle with a coupling member so that the measurement block may be urged against the road surface; detecting, using the angle detection means, a displacement angle between the first and second coupling rods each time the measurement block moves by one pitch, which is a center-to-center distance between the rollers, in a longitudinal direction of the road surface as the measurement vehicle moves; and creating a longitudinal profile of the road surface based on detected angle values.
In this configuration of the first aspect of the present invention, the measurement block is constituted of the disk-shaped first, second, and third rollers having the same outer diameter with a predetermined spacing set therebetween and the first and second coupling rods which couples these rollers in a revolving manner, so that each time the measurement block moves by the one pitch in a longitudinal direction of the road, positions where the first and second rollers were placed before the movement are occupied by the second and third rollers respectively after the movement. Therefore, each time such measurement block moves by the one pitch, a displacement angle between the first and second coupling rods can be detected by the angle detection means to thereby use an inclination angle at a measurement starting position as a longitudinal profile initial value in order to sequentially obtain a change in angle of the first and second coupling rods based on this value, thus obtaining a longitudinal road surface profile automatically and sequentially. In such a manner, this sequential-two-angles method is so called because it uses a measurement block constituted of first, second, and third rollers coupled by first and second coupling rods to enables, from a new viewpoint, measurement which has been possible by means of a sequential-three-points method of using three displacement gages arranged in parallel with each other based on the conventional sequential-two-points method. As a result, by the present invention, two angles can be detected sequentially to thereby create longitudinal road surface profile easily and accurately as compared with the conventional sequential-two-points method or the auto-collimator method. Moreover, by using roller in such a manner, it is possible to accurately measure flatness of a road surface as a whole without being affected by fine irregularities even if the road surface has them as in the case of draining pavement.
A second aspect of the present invention provides a method comprising the steps of: moving, in a unit of a predetermined spacing, a measuring instrument constituted of three probes aligned in parallel with each other with a predetermined spacing therebetween along a longitudinal profile according to the above-mentioned claim 1 in a condition where probes on both sides of the measuring instrument are kept in contact with the longitudinal profile; obtaining a deflection dimension of an intermediate probe of the measuring instrument with respect to the longitudinal profile for each of the movement units; and calculating a standard deviation of a measurement value of the deflection dimension to thereby provide flatness of a road surface.
In the second aspect of the present invention, the measuring instrument constituted of the three probes aligned in parallel with each other with the predetermined spacing therebetween can be used to easily obtain flatness of a road surface based on a longitudinal profile obtained by the measurement method described in claim 1. Preferably, software processing by use of a microcomputer is conducted to obtain a precise result rapidly.
A third aspect of the present invention provides a method comprising the steps of: moving a measuring instrument constituted of a deadweight having a predetermined weight attached to one end of a linear spring material having a predetermined spring constant longitudinally at a predetermined speed in a condition where the linear spring material is poised as erected with the deadweight as arranged at an upper end thereof and a lower end thereof is kept in contact with a longitudinal profile described in the first aspect of the present invention; integrating longitudinal displacements of the deadweight during the movement; and calculating an integrated value of the displacements to provide flatness of the road surface.
This flatness evaluation method is referred to as the International Roughness Index (iRi) method.
In the third aspect of the present invention, in accordance with the iRi, it is possible to obtain practical roughness of a road surface as viewed from a vehicle travelling on a road. A precise result of the iRi can be obtained rapidly and accurately also preferably by conducting software processing by use of a microcomputer.
A fourth aspect of the present invention provides a longitudinal road surface profile measurement method for surveying a longitudinal irregularity condition in a road surface while moving a measurement vehicle longitudinally on a road, comprising the steps of: arranging first, second, and third disk-shaped rollers having the same outer diameter so that the rollers have a predetermined spacing therebetween on the same straight line and rotate in the same straight-line direction; using a measurement block constituted of a first predetermined-length coupling rod which is mounted on rotary shafts of the first and second rollers to couple the first and second rollers in a revolving manner, a second coupling rod which is mounted on rotary shafts of the second and third rollers to couple the second and third rollers in a revolving manner, distance measurement means which measures a movement distance of the rollers, and angle detection means which detects a displacement angle by which the first and second coupling rods have revolved from a straight state thereof, to elastically attach the measurement block to a measurement vehicle with a coupling member so as to be urged against the road surface; deciding a plurality of survey positions obtained as a result of dividing into a plurality of pitches a reference distance which is defined as a center-to-center dimension between the first and third rollers in a condition where the first and second coupling rods are in a straight state; each time the leading roller reaches the survey positions sequentially in an advancing direction in which the measurement block moves over the reference distance in a longitudinal direction of the road surface, detecting a displacement angle between the first and second coupling rods at each of the survey positions using the angle detection means; calculating height data of the road surface at each of the survey positions using a filter operation method based on the detected displacement angle value obtained by the angle detection means and known height data at each of the immediately preceding survey positions measured by the measurement block, to obtain a unit road surface profile over the reference distance; and integrating the consecutive unit road surface profiles in the entire longitudinal direction of the road surface, to create a longitudinal profile of the road surface.
In the fourth aspect of the present invention, the measurement block starts moving from a starting point by as much as a distance that corresponds to the reference distance in the longitudinal direction of the road surface. In this case, each time the leading roller reaches each of the pre-determined survey positions within the reference distance sequentially, a displacement angle between the first and second coupling rods at each of the survey positions is detected by the angle detection means. Based on the detected value obtained by this angle detection means and known height data at each of the survey positions measured by the measurement block at the survey position immediately preceding the current angle detection position, height data can be calculated at each of the survey positions sequentially using the filter operation method. By integrating the calculated data measured at each of the survey positions, a road surface profile within the reference distance can be accurately obtained for each of the survey positions having a short pitch therebetween. The unit road surface profiles thus obtained within the reference distance can be integrated consecutively in the entire longitudinal direction of the road surface, to obtain a precise longitudinal profile of the entire road surface.
As a result, according to the fourth aspect of the present invention, precise data of irregularities of a road surface can be obtained for each of short pitches between the survey positions into which the reference distance is divided, so that it is possible to accurately detect irregularities in the entire road surface including small irregular objects such as a structure joint, a concrete bond, and a pot-hole which are present on the entire road surface as a whole. Furthermore, the road surface profile thus obtained can be utilized in road step management etc.
The following will describe a method using an Infinite Impulse Response Filter (hereinafter abbreviated as IIR filter) as one example of the filter operation method.
It is supposed, as shown in FIG. 8, that the first and second coupling rods 14 and 15 (which have the same length in this case) are in a straight state, a reference distance 50 (in an arbitrary unit), which is a center-to-center distance between the first and third rollers 11 and 13, is divided into, for example, 50 equal pitches, and each survey position is i through (i-50). If each height of the road surface that corresponds to each of the survey positions is y(i) through y(i-50), an angle u(i) between the first and second coupling rods 14 and 15 is represented by the following equation 1:                               u          ⁢                      (            i            )                          =                              1            a                    ⁢                      (                                          y                ⁢                                  (                  i                  )                                            -                              2                ⁢                                  y                  ⁢                                      (                                          i                      -                      25                                        )                                                              +                              y                ⁢                                  (                                      i                    -                    50                                    )                                                      )                                              (                  Equation          ⁢                      xe2x80x83                    ⁢          1                )            
where ┌a┘ is a constant.
Equation 1 can be transformed into the following equation 2 represented by y(i):
y(i)=2y(ixe2x88x9225)xe2x88x92y(ixe2x88x9250)+au(i)xe2x80x83xe2x80x83(Equation 2).
By conducting z-transformation on the above-mentioned equation 1, the following equation 3 is given. Furthermore, Equation 3 can be transformed into the following equation 4 represented by Y(z):                               U          ⁢                      (            z            )                          =                              1            a                    ⁢                      (                          1              -                              2                ⁢                                  z                                      -                    25                                                              +                              z                                  -                  50                                                      )                    ⁢                      Y            ⁢                          (              z              )                                                          (                  Equation          ⁢                      xe2x80x83                    ⁢          3                )                                          Y          ⁢                      (            z            )                          =                                            az              50                                                      z                50                            -                              2                ⁢                                  z                  25                                            +              1                                ⁢                      U            ⁢                          (              z              )                                                          (                  Equation          ⁢                      xe2x80x83                    ⁢          4                )            
Equation 4 is developed with its denominator as assumed to be D(z), into Equation 5. Furthermore, if Equation 5 is expressed by a product of D1(z) and D2(z), D1(z) and D2(z) can be summarized as given in Equation 6:
D(z)=z50xe2x88x922z25+1=(zxe2x88x921)2.(z48+2z47+ . . . +24z25+25z24+24z23+ . . . +1)xe2x80x83xe2x80x83(Equation 5)
                                                                                          D                  1                                ⁡                                  (                  z                  )                                            =                                                (                                      z                    -                    1                                    )                                2                                                                                                                          D                  2                                ⁡                                  (                  z                  )                                            =                                                z                  48                                +                                  2                  ⁢                                      z                    47                                                  +                …                +                                  24                  ⁢                                      z                    25                                                  +                                  25                  ⁢                                      z                    24                                                  +                                  24                  ⁢                                      z                    23                                                  +                …                +                1                                                                                        =                                                ∏                                      i                    =                    1                                    24                                ⁢                                  xe2x80x83                                ⁢                                                      (                                          z                      -                                                                        ⅇ                          j                                                ⁢                                                                              2                            ⁢                            π                                                    25                                                ⁢                        i                                                              )                                    2                                                                                                        j              =                                                -                  1                                                                                        (                  Equation          ⁢                      xe2x80x83                    ⁢          6                )            
A solution of D(z)=0, that is, a pole Pk of the filter, corresponds to two 1s and two of each e[j(2xcfx80/25)1](i=1 to 25), that is, a sum of irregularities between 1 and 25. The behavior of this pole Pk is represented by (i, i(Pk)i), so that any pole has an absolute value of 1 and an output of the filter having D(z) as its denominator diverges.
Accordingly, by conducting substitution on the pole as given by the following equation 7, the filter output can be converged:                                           poles            ⁢                          :                        ⁢            1                    →                                    P              ⁢                              xe2x80x83                            ⁢              O                         less than             P             less than             1                          ⁢                  
                ⁢                              ⅇ                          j              ⁢                                                2                  ⁢                  π                                25                            ⁢              i                                →                                                    Wa                ·                                  ⅇ                                      j                    ⁢                                                                  2                        ⁢                        π                                            25                                        ⁢                    i                                                              ⁢                              xe2x80x83                            ⁢              O                         less than             Wa             less than             1                                              (                  Equation          ⁢                      xe2x80x83                    ⁢          7                )            
By replacing the poles of the above-mentioned D1(z) and D2(z) with each other based on Equation 7, D1(z) and D2(z) are obtained as shown in Equations 8 and 9:
D1xe2x80x2(z)=(zxe2x88x92P)2=z2xe2x88x922Pzxe2x88x92P2xe2x80x83xe2x80x83(Equation 8)
                                                                                          D2                  xe2x80x2                                ⁡                                  (                  z                  )                                            =                              xe2x80x83                            ⁢                                                ∏                                      i                    =                    1                                    24                                ⁢                                  xe2x80x83                                ⁢                                                      (                                          z                      -                                              Wa                        ·                                                  ⅇ                                                      j                            ⁢                                                                                          2                                ⁢                                π                                                            25                                                        ⁢                            i                                                                                                                )                                    2                                                                                                        =                              xe2x80x83                            ⁢                                                z                  48                                +                                  2                  ⁢                                      waz                    47                                                  +                …                +                                  24                  ⁢                                      wa                    23                                    ⁢                                      z                    25                                                  +                                  25                  ⁢                                      wa                    24                                    ⁢                                      z                    24                                                  +                                                                                                        xe2x80x83                            ⁢                                                24                  ⁢                                      wa                    26                                    ⁢                                      z                    23                                                  +                …                +                                  wa                  48                                                                                        (                  Equation          ⁢                      xe2x80x83                    ⁢          9                )            
Furthermore, D1(z) and D2(z) can be multiplied by each other, D(z) to give D(z) as shown in Equation 10:
Dxe2x80x2(z)=D1xe2x80x2(z).D2xe2x80x2(z)=z50+C1z49+C2z48+ . . . +C49Z+C50xe2x80x83xe2x80x83(Equation 10)
where C1 through C50 are constants.
D(z) given above can be replaced by D(z) in the above-mentioned Equation 4 to obtain the following Equation 11, which can be represented by U(z) to provide Equation 12:                               Y          ⁢                      (            z            )                          =                                            az              50                                                      D                xe2x80x2                            ⁢                              xe2x80x83                            ⁢                              (                z                )                                              ·                      U            ⁢                          (              z              )                                                          (                  Equation          ⁢                      xe2x80x83                    ⁢          11                )                                          U          ⁢                      (            z            )                          =                              1            a                    ·                                    D              xe2x80x2                        ⁢                          (              z              )                                ·                      z                          -              50                                ·                      Y            ⁢                          (              z              )                                                          (                  Equation          ⁢                      xe2x80x83                    ⁢          12                )            
By conducting inverse z-transformation on this equation 12, Equation 13 can be obtained which indicates a displacement angle u(i) between the first and second coupling rods 14 and 15 at the survey position i. Furthermore, Equation 13 can be represented by y(i) to provide Equation 13 indicating y(i), which indicates a road surface height at the survey position i:                               u          ⁢                      (            i            )                          =                              1            a                    ⁢                      (                                          y                ⁢                                  (                  i                  )                                            +                                                C                  1                                ⁢                                  y                  ⁢                                      (                                          i                      -                      1                                        )                                                              +                                                C                  2                                ⁢                                  y                  ⁢                                      (                                          i                      -                      2                                        )                                                              +              …              +                                                C                  50                                ⁢                                  y                  ⁢                                      (                                          i                      -                      50                                        )                                                                        )                                              (                  Equation          ⁢                      xe2x80x83                    ⁢          13                )            xe2x80x83y(i)=C1y(ixe2x88x921)xe2x88x92C2y(ixe2x88x922)xe2x88x92 . . . xe2x88x92C50y(ixe2x88x9250)+au(i)xe2x80x83xe2x80x83(Equation 14)
That is, by employing the IIR Method, an operation equation for calculating a longitudinal road surface profile is given in Equation 14. By dividing the reference distance into a plurality of small pitches and using this operation equation, it is possible to obtain data of the height at each of the survey positions from the displacement angle u(i) and known height data of each of the immediately preceding survey positions of the measurement block.